Tech Stack Research

[BLOCKING] Execute skill steps in declared order. NEVER skip, reorder, or merge steps without explicit user approval. [BLOCKING] Before each step or sub-skill call, update task tracking: set in_progress when step starts, set completed when step ends. [BLOCKING] Every completed/skipped step MUST include brief evidence or explicit skip reason. [BLOCKING] If Task tools are unavailable, create and maintain an equivalent step-by-step plan tracker with the same status transitions.

Quick Summary

Goal: Deliver user-confirmed, per-layer tech stack — each choice backed by 3+ researched options, weighted scoring, cited evidence, confidence % — by acting as solution architect: derive technical requirements from business analysis, research current market, produce detailed comparison report, so team commits to stack fit for scale, budget, skills, timeline, NOT familiarity.

Summary:

• Purpose: act as solution architect — derive technical requirements from business analysis, research current market, produce per-layer comparison report so team commits to stack fit for scale/budget/skills/timeline, NOT familiarity.
• All 7 main steps (run in order): (1) Load Business Context → (2) Derive Technical Requirements + user-confirm → (3) Research Per Layer (WebSearch 3+ options each) → (4) Deep Comparison Matrix → (5) Weighted Score & Ranking → (6) Generate Report → (7) User Validation Interview.
• Requirements BEFORE research: load prior business/domain/PBI artifacts (Step 1), map business signals → technical requirements (Step 2), gate on user confirmation (AskUserQuestion) before any WebSearch (Step 3).
• Evaluate every stack layer (backend, frontend, database, messaging, infra, auth) independently — minimum 3 WebSearched options per layer, each with cited evidence (URL, benchmark, case study), NEVER familiarity (Steps 3-4).
• Score with weighted 8-criteria matrix (High=3x / Medium=2x / Low=1x), rank each layer with confidence %; capped <=200-line report → {plan-dir}/research/tech-stack-comparison.md (Steps 5-6).
• End-of-skill user validation interview (5-8 questions) mandatory, NEVER skipped — only confirmed decisions written to phase-02-tech-stack.md as status: confirmed (Step 7).

Workflow:

1. Load Business Context — Read business evaluation, domain model, refined PBI artifacts
2. Derive Technical Requirements — Map business needs to technical constraints
3. Research Per Layer — WebSearch top 3 options for each stack responsibility
4. Deep Compare — Pros/cons matrix, benchmarks, community health, team fit
5. Score & Rank — Weighted scoring across 8 criteria
6. Generate Report — Structured comparison report with recommendation
7. User Validation — Present findings, ask 5-8 questions, confirm choices

Key Rules:

• MANDATORY IMPORTANT MUST ATTENTION research minimum 3 options per stack layer
• MANDATORY IMPORTANT MUST ATTENTION include confidence % with evidence for every recommendation
• MANDATORY IMPORTANT MUST ATTENTION run user validation interview at end (NEVER skip)
• All claims must cite sources (URL, benchmark, case study)
• Recommend on benchmarked evidence (URL, benchmark, case study); NEVER on familiarity alone

Be skeptical. Apply critical thinking, sequential thinking. Every claim needs traced proof, confidence percentages (Idea should be more than 80%).

Step 1: Load Business Context

Read artifacts from prior workflow steps (search plans/, team-artifacts/):

• Business evaluation report (viability, scale, constraints)
• Domain model / ERD (complexity, entity count, relationships)
• Refined PBI (acceptance criteria, scope)
• Discovery interview notes (team skills, budget, timeline)

Extract and summarize:

Step 2: Derive Technical Requirements

Map business signals to technical requirements:

MANDATORY IMPORTANT MUST ATTENTION validate derived requirements with user via AskUserQuestion before proceeding to research.

Step 3: Research Per Stack Layer

For EACH layer, research top 3 options via WebSearch (minimum 5 queries total):

Stack Layers to Evaluate

WebSearch Queries (minimum 5 per layer)

"{option_A} vs {option_B} {current_year} comparison"
"{option} enterprise production case studies"
"{option} community size github stars"
"{option} performance benchmarks {use_case}"
"{option} security track record vulnerabilities"

Step 4: Deep Comparison Matrix

For EACH stack layer, produce comparison table:

Scoring: 1-5 scale. Weight: High=3x, Medium=2x, Low=1x.

Per-Option Detail Block

For each option, document:

### {Layer}: {Option Name}

**Pros:**

- {Pro 1} — {evidence/source}
- {Pro 2} — {evidence/source}
- {Pro 3} — {evidence/source}

**Cons:**

- {Con 1} — {evidence/source}
- {Con 2} — {evidence/source}

**Best suited when:** {conditions}
**Not suitable when:** {conditions}
**Production examples:** {2-3 real companies using this}

Step 5: Weighted Score & Ranking

Calculate weighted total per option per layer. Present ranking:

### {Layer} Ranking

1. **{Option A}** — Score: {X}/100 — Confidence: {Y}%
2. **{Option B}** — Score: {X}/100 — Confidence: {Y}%
3. **{Option C}** — Score: {X}/100 — Confidence: {Y}%

**Recommendation:** {Option A}
**Why:** {2-3 sentence rationale linking to team skills, scale, and constraints}

Step 6: Generate Report

Write report to {plan-dir}/research/tech-stack-comparison.md with:

1. Executive summary (recommended full stack in 5 lines)
2. Technical requirements table (from Step 2)
3. Per-layer comparison matrices (from Step 4)
4. Per-layer rankings with recommendations (from Step 5)
5. Combined recommended stack diagram
6. Risk assessment for recommended stack
7. Alternative stack (second-best combo) for comparison
8. Unresolved questions

Report must be <=200 lines. Use tables over prose.

Step 7: User Validation Interview

MANDATORY IMPORTANT MUST ATTENTION present findings and ask 5-8 questions via AskUserQuestion:

Required Questions

1. Per-layer recommendation confirmation — "For {layer}, I recommend {option}. Agree?"
   • Options: Agree (Recommended) | Prefer {option B} | Need more research
2. Risk tolerance — "The recommended stack has {risk}. Acceptable?"
3. Team readiness — "Team needs to learn {X}. Training plan needed?"
4. Budget alignment — "Estimated infra cost: ${X}/month. Within budget?"
5. Timeline fit — "This stack enables MVP in {X} months. Acceptable?"

Optional Deep-Dive Questions (pick 2-3 based on context)

• "Should we consider {emerging tech} for {layer}?"
• "Any compliance requirements I haven't captured?"
• "Preference for managed services vs self-hosted?"
• "Monorepo or polyrepo for this team size?"

After user confirms, update report with final decisions, mark status: confirmed.

Output

{plan-dir}/research/tech-stack-comparison.md    # Full comparison report
{plan-dir}/phase-02-tech-stack.md               # Final confirmed tech stack decisions

MANDATORY IMPORTANT MUST ATTENTION break work into small todo tasks using TaskCreate BEFORE starting. MANDATORY IMPORTANT MUST ATTENTION validate EVERY recommendation with user via AskUserQuestion — NEVER auto-decide. MANDATORY IMPORTANT MUST ATTENTION include confidence % and evidence citations for all claims. MANDATORY IMPORTANT MUST ATTENTION add a final review todo task to verify work quality.

Next Steps

MANDATORY IMPORTANT MUST ATTENTION — NO EXCEPTIONS after completing this skill, you MUST ATTENTION use AskUserQuestion to present these options. Do NOT skip because task seems "simple"/"obvious" — the user decides:

• "/architecture-design (Recommended)" — Design solution architecture with chosen tech stack
• "/plan" — If architecture already decided
• "Skip, continue manually" — user decides

Council escalation (always-offer, second prompt)

After the existing ## Next Steps prompt above resolves, present a second, independent AskUserQuestion call:

• "Skip council — proceed with chosen stack (Recommended)" — Continue with the selected tech stack as-is.
• "Escalate to /llm-council" — Run 11 sub-agent council. Best applied when 2+ stacks score within 15% on the comparison matrix or you have unfamiliar/strategic dependencies. Cheaper alternatives: /why-review, /plan-validate.

Scenario Stress & Resilience Evaluation — CONDITIONAL, evidence-gated, business-criticality-aware. The top-down companion to SYNC:scale-technique-gate: instead of "is technique X present?", put the system UNDER concrete failure/load scenarios and judge whether it SURVIVES, SELF-HEALS, and whether its BUSINESS needs it to. ADVICE-ONLY: emit the Scenario Stress Matrix as guidance; NEVER mutate any score, verdict band, or gate pass/fail.

1. Reuse the scale tier derived by SYNC:scale-technique-gate (or derive it identically from evidence); also derive business-criticality B0–B3 from specs/SLA/product docs + the domain, cite file:line + confidence. B0 best-effort · B1 important · B2 business-critical · B3 mission-critical/regulated. Unknown → state the assumption, do NOT default to B3/T3. Criticality-signal floor (both-directions safety): regulated / PII / financial / health data, money movement, auth/identity, or legal-compliance scope raises B to at least B2 even absent SLA/SLO docs; anti-over-engineering lowers hardening ONLY when NO such signal is present. B (blast if it fails) and T (scale of load/data) are independent — a low-traffic payroll run is low-T, high-B.
2. Select in-scope scenarios — only those the system's B/T combination warrants (a B0 internal PoC skips region-loss/DR entirely; a B3/T0 regulated service still needs backups + DR by BUSINESS, not scale).
3. Walk each in-scope scenario: simulate the stimulus → trace the break path → name the failure signature → answer the self-heal/recovery question (auto-recover? MTTR? manual runbook?) → name the trade-off it forces. Families: traffic spike · sustained growth · data-volume growth · write/ingest burst · dependency down/slow · instance/node loss · zone/region loss · data loss/corruption · poison-message/retry-storm · cascading failure/backpressure · cold-start/deploy-blip · clock-skew/duplicate-delivery.
4. Assign one verdict per scenario: WITHSTANDS · DEGRADES-GRACEFULLY · FAILS-HARD (→ advise only) · N/A-by-business (not warranted → skip, not a gap) · OVER-HARDENED (resilience beyond business need → advise AGAINST, cite carrying cost).
5. Anti-over-engineering guard (first-class): a lean system whose business does not need HA/DR is a PASS; OVER-HARDENED flags resilience the business does not warrant. This guard is symmetric with the criticality-signal floor above — never under-harden a B2+ system just because its traffic is low.
6. Output — Scenario Stress Matrix: scenario | in-scope (B/T)? | verdict | self-heal | trade-off | evidence (file:line/config/infra). Full catalog + Business×Scale in-scope baseline + verdict/tier tables → .claude/docs/scenario-stress-catalog.md. ADVISORY-ONLY: NEVER mutate any /20, /24, verdict band, or gate pass/fail. Drift-guard: scenarios/verdicts/business-tiers are AUTHORITATIVE in the catalog — update it FIRST, then re-run .claude/scripts/inject_scenario_stress_gate.py. Scale tier stays single-sourced in scale-technique-catalog.md.

BLOCKED until: - [ ] scale tier + business-criticality (with criticality-signal floor) derived from evidence - [ ] in-scope scenarios selected - [ ] matrix emitted - [ ] over-hardening guard applied - [ ] advisory-only (no score/verdict mutation) confirmed

Engineering Foundation Gate — CONDITIONAL, evidence-gated, profile-tiered. Judges the PROJECT'S ENGINEERING FOUNDATION: can this team build, run, test and change the system safely — anywhere, repeatably, as it grows? Its companions judge the running system's DESIGN (scale-technique-gate: is technique X present? · scenario-stress-eval: does it survive scenario Y?) — a system can score perfectly on both while nobody but its author can build it. State OUTCOMES, never tools: detect the stack, research the current ecosystem, present 2–3 options, the user decides, record the decision — best practice turns over, the outcome does not.

1. Derive the project profile FIRST — from evidence, never assumed. Lifecycle G greenfield (foundation being created) / B brownfield (foundation exists, under audit) · scale T0–T3 (reuse scale-technique-catalog.md, never re-derive) · criticality B0–B3 with its criticality-signal floor (reuse scenario-stress-catalog.md) · repo shape R0 single module / R1 few (2–5) / R2 many modules, multi-team / R3 monorepo estate · runtime surface. Cite file:line/config/CI + confidence. Unknown axis → state the assumption and take the LOWER tier; NEVER default to T3/B3/R3 — an over-stated profile turns this gate into busywork a small team correctly ignores.
2. Judge all 7 dimensions — always all 7, never a filtered subset (an omitted row is indistinguishable from an overlooked one). Depth belongs to the named owner; this gate decides only present/absent:
   • F1 Reproducible environment (ALL profiles — the floor) — one documented path takes a clean machine to a running system; toolchain versions pinned; dependencies locked to exact versions; every external prerequisite declared with a way to obtain or fake it; config environment-injected, never machine-implicit; build deterministic. This is what kills "works on my machine" — not carelessness, but a build depending on ambient state nobody declared. → scaffold · architecture-scalability-review
   • F2 Dual execution modes (T1+, multi-contributor, or containerized target; B2+ regardless of scale) — the system runs on the bare host AND fully containerized from ONE source of truth for config and topology, and the suites run in BOTH directions (host-run against a containerized system, and wholly inside a container). Both modes exercised, so neither rots. Host mode buys a fast inner loop and a debugger; container mode buys CI/production parity and a trustworthy day one — a project with only one teaches people to work around it undocumented. A mode honestly dropped with a stated reason is N/A; the defect is the claimed-but-rotten mode. → scaffold · devops · production-readiness-review
   • F3 Environment-portable tests (local+CI all profiles; production-shaped T1+/B2+) — the SAME suites run against local, CI and production-like targets, parameterized by configuration, never by forked test code (only one fork ever stays maintained, so forking guarantees divergence). Missing capability reports ENVIRONMENT-BLOCKED rather than silently passing; unsafe-in-production tests are excluded by an enforced mechanism whose absence fails loudly, not by a convention someone must remember. "Runs in prod" means a safe, declared, NON-MUTATING subset. → test-architecture-execution-contract · integration-test-review
   • F4 Test-strength proof (wherever tests exist) — evidence the suite actually fails when the code is wrong; a passing suite means nothing until it is known to be capable of failing for the right reason. Strongest available first: (a) automated fault injection scoped to CHANGED code — a surviving defect is a missing or vacuous assertion; gate on it where the ecosystem offers a workable tool. (b) Deliberate defect-seeding drill — the universal fallback, needing no tooling and available in every ecosystem: break the production code behind a top invariant, run the suite, record WHICH NAMED TEST went red, restore. Nothing went red ⇒ that behavior has no protection — write the killing test. (c) Assertion-intent audit: flag assertions that would still hold under an inverted implementation, that assert only non-nullness or a type, that re-assert the input, or that assert infrastructure bookkeeping instead of the outcome the system owns. Line coverage is a DIAGNOSTIC, never a gate — low coverage is a useful negative signal; high coverage is not evidence of quality, and gating on the percentage reliably produces tests written to touch lines rather than protect behavior. Scope boundary — do NOT re-litigate a solved question: this gate asks only whether the PROJECT HAS a test-strength mechanism wired into its harness at all; PER-CHANGE enforcement is already owned by integration-test-review Gate 1's Mutation Probe Ledger (tool path + manual fallback, ledger required either way). Report the setup gap here, the assertion gap there, never both. → harness-setup (sensor design) · integration-test-review (per-change enforcement)
   • F5 Performance & scale-under-data (T1+/B2+ for a real tier; T0/B0 = one documented largest-expected-volume check) — performance MEASURED by something that RUNS and CAN FAIL, not reasoned about. The companion gates can be fully satisfied by a system that has never once been run against a large dataset; this is the executable counterpart. Requires: a runnable perf tier with a documented command (it belongs in the tier matrix); on-demand realistic volume AND realistic shape — distribution, cardinality, skew, not a million identical rows; named latency/throughput/memory budgets the run ASSERTS (a perf test that only reports numbers is a dashboard, and eventually nobody reads it); growth compared across ≥2 volumes ~10× apart, because one data point cannot distinguish O(n) from O(n²); and resource exhaustion as a tested, bounded outcome — backpressure, paging or a clean error rather than an OOM kill, with unbounded result-sets, unbounded in-memory accumulation and unbounded concurrency provably absent or bounded on the paths that matter. State whether a number is a regression signal or a capacity statement. → performance-review · seed-test-data
   • F6 Build & change scalability (R1+ declared style + boundaries; R2+ computable affected set, enforced checks, measured incrementality) — build/test cost and blast radius do NOT grow with the codebase. Every project is fast on day one; the foundation question is whether the tenth module costs what the second did. Requires: the affected module/sub-domain set is COMPUTABLE because inter-module dependencies are explicit and declared; incrementality and caching are real and measured (claimed caching that never hits is an invisible failure); boundaries enforced MECHANICALLY, since unenforced boundaries decay silently until the affected set is "everything"; a declared architecture style (modular monolith / clean / hexagonal / layered — which one matters far less than that one is declared, written down and enforced, because an undeclared style is indistinguishable from none after two years); implementation hidden behind abstraction so a technology swaps without touching business code (depth → complexity-prevention); and a fast scoped inner-loop check — if the only available check is the slow exhaustive one, that is the finding. Scope boundary: architecture-scalability-review G2 Build & CI Scalability already SCORES incremental/affected-only/caching/monorepo posture and G4 scores boundary enforcement — where that review has run, cite its verdict rather than re-scoring; this gate only confirms the dimension was examined and is not silently absent. → architecture-scalability-review (G2/G4 depth) · architecture-review (diff-level boundary drift) · complexity-prevention (cost of change in the code itself)
   • F7 Mechanical quality harness (format + lint + type/static analysis + build/test at ALL profiles; architecture-fitness R1+; dependency health + secret scanning wherever real data ships, unconditional at B2+; complexity/duplication + drift R1+/T1+) — no human reviewer spends attention on a defect class a machine could have caught; reviewer attention is the scarcest resource in the project. Account for EVERY class or record it N/A with a reason — an unlisted class is an unexamined one: formatting · lint/correctness · type & static analysis · complexity & duplication · executable architecture-fitness · dependency vulnerability & license · secret scanning · build/test gates plus the F4 signal · documentation/config drift. Local and CI must run the SAME command, configuration and version (divergence means CI failures nobody can reproduce); checks must ENFORCE, not warn (an unread warning stream is not a harness); strictest reasonable defaults, loosened only with a recorded reason, since a large silent suppression list is itself a finding; cheap checks first, expensive last. Brownfield adoption uses a ratchet — fail on NEW violations, tolerate the existing baseline — which counts as PRESENT, not partial, because it stops regression from day one. → linter-setup · harness-setup · security-review
3. Assign one verdict per dimension: PRESENT (achieved and proven by cited evidence) · MISSING-WARRANTED · PARTIAL-WITH-PATH (gap named + concrete incremental step) · N/A-by-profile (below the warranting profile — a correctly-lean project is a PASS here, never a gap; never report it as a deficiency) · OVER-ENGINEERED (present but unwarranted → advise AGAINST, name the carrying cost) · UNVERIFIED (could not be checked — say so honestly; NEVER score an unverified dimension PRESENT).
4. Authority is context-split — the one place this gate differs from its two companions. CREATING a foundation (greenfield init, scaffold, a plan standing up build/test/CI) → a MISSING-WARRANTED dimension is BLOCKING: you are choosing the foundation right now, so omitting a warranted one must be an explicit decision, not a silent default. AUDITING an existing foundation (brownfield review, architecture audit, changes review) → ADVISORY ONLY: emit the matrix plus a prioritized adoption path and NEVER mutate any score, /20, /24, verdict band, or gate PASS/FAIL. — why the split: the cost of adding a foundation is near zero at creation and high afterwards, so strictness should track that cost; blocking a review of a ten-year-old codebase on foundations it never had produces a useless report, not a better project.
5. Anti-over-engineering guard (first-class, and symmetric). Do NOT demand a container mode of a single-author local utility, a distributed load-generation platform for a small internal service, affected-set computation or boundary enforcement for a single module, or four overlapping analyzers reporting one defect class (the carrying cost is noise and slow builds, and people learn to ignore the output). Splitting a small system into many modules to look modular buys a distributed monolith — the coupling survives the split while the build cost doubles; the trigger is real module and team count, never aesthetics. Symmetric with the criticality floor: never UNDER-harden a B2+ system merely because its traffic is low.
6. Every brownfield finding names the smallest next step that is valuable on its own. Seven MISSING-WARRANTED verdicts with no first step is a demoralizing document nobody acts on. Default ladder, each rung independently valuable and making the next cheaper: pin the toolchain & commit the lockfile → make one local command that CI also runs → ratchet the harness on (fail-on-new) → run the defect-seeding drill on the top invariants → repair the missing execution mode → seed a realistic volume and assert ONE budget → declare the style, then enforce dependency direction. Deviate on evidence, and say why; what is not acceptable is a gap list with no first step.
7. Output — Foundation Readiness Matrix: dimension | warranted at this profile? | present? | verdict | evidence (file:line/config/CI) | smallest next step, preceded by the derived profile with per-axis evidence and confidence, followed by the ordered adoption path (brownfield) or the blocking list (greenfield). Full catalog — per-dimension proof lists, warranting matrix, adoption ladder → .claude/docs/engineering-foundation-catalog.md. Drift-guard: profile axes, dimensions, verdicts and warranting tiers are AUTHORITATIVE in that catalog — update it FIRST, then re-run .claude/scripts/inject_engineering_foundation_gate.py to re-propagate. Scale tier stays single-sourced in scale-technique-catalog.md; business criticality in scenario-stress-catalog.md.

BLOCKED until: - [ ] profile derived from evidence (lifecycle + T + B + R, lower tier when unknown) - [ ] all 7 dimensions judged, none omitted - [ ] matrix emitted with file:line/config/CI evidence - [ ] anti-over-engineering guard applied - [ ] authority confirmed — creating ⇒ blocking, auditing ⇒ advisory-only with no score mutation - [ ] every brownfield gap carries a smallest-next-step

IMPORTANT MUST ATTENTION scale-technique gate: derive the scale tier from evidence FIRST (T0 internal · T1 <10k · T2 10k–1M · T3 millions+), then judge each warranted technique PRESENT/MISSING-WARRANTED/N/A-by-scale/OVER-ENGINEERED. Advise on warranted-but-missing gaps AND advise AGAINST unwarranted heavyweight techniques (anti-over-engineering). ADVICE-ONLY — emit the Technique Applicability Matrix as guidance; NEVER mutate any score, verdict band, or gate pass/fail. Full catalog → .claude/docs/scale-technique-catalog.md (authoritative for tier thresholds & per-technique warranting tiers — on any change update the catalog FIRST, then re-run inject_scale_technique_gate.py).

IMPORTANT MUST ATTENTION scenario-stress gate: reuse the scale tier T0–T3 AND derive business-criticality B0–B3 from evidence first — apply the criticality-signal floor (regulated/PII/financial/health data · money movement · auth/identity · legal-compliance → at least B2 even absent SLA docs; do NOT default to B3). Select only the scenarios the B/T combination warrants, then walk each (simulate → trace → failure signature → self-heal/MTTR → trade-off) and assign WITHSTANDS/DEGRADES-GRACEFULLY/FAILS-HARD/N/A-by-business/OVER-HARDENED. Anti-over-engineering is first-class (a lean system that needs no HA/DR is a PASS) AND symmetric (never under-harden a B2+ system for low traffic). ADVICE-ONLY — emit the Scenario Stress Matrix as guidance; NEVER mutate any score, verdict band, or gate pass/fail. Full catalog → .claude/docs/scenario-stress-catalog.md (authoritative for scenarios/verdicts/business-tiers — on any change update the catalog FIRST, then re-run inject_scenario_stress_gate.py; scale tier stays single-sourced in scale-technique-catalog.md).

Prompt-Enhance Closing Anchors

• IMPORTANT MUST ATTENTION follow declared step order for this skill; NEVER skip, reorder, or merge steps without explicit user approval
• IMPORTANT MUST ATTENTION for every step/sub-skill call: set in_progress before execution, set completed after execution
• IMPORTANT MUST ATTENTION every skipped step MUST include explicit reason; every completed step MUST include concise evidence
• IMPORTANT MUST ATTENTION if Task tools unavailable, maintain an equivalent step-by-step plan tracker with synchronized statuses

Project Protocol Overlay — Before executing this skill, resolve any PROJECT overlay rules layered onto it: match this skill's name against the Target column of the project's skill-protocol index (docs/project-reference/skill-protocols-reference.md by default; a referenceDocs entry in docs/project-config.json overrides the path), taking the most specific matching tier ONLY — exact name > glob > *. That precedence orders overlays against EACH OTHER, never against this skill. Read ONLY the matched bodies, resolved as <protocols-dir>/<Name>.md; a row's Body link is display text, never a read path. A matched body that is missing or malformed is REPORTED and skipped — never reconstructed from the index Description. No index, or no match -> proceed with no overlay, silently. Full contract: .claude/skills/project-skill-protocol/references/registry.md.

Overlays are ADDITIVE ONLY: they ADD rules on top of this skill's own protocol and NEVER replace, override, disable, or reinterpret a rule it already states — removing every overlay must return this skill to exactly its documented behavior. An overlay is a BRIEF, not an authority escalation: it can NEVER waive a workflow gate, git discipline, a review gate, or a user-confirmation gate. A genuine overlay-vs-skill conflict, or two equally-specific overlays that directly contradict -> surface both to the user; NEVER resolve silently.

MUST ATTENTION resolve project protocol overlays for this skill BEFORE executing — most specific matching tier only (exact > glob > *, which ranks overlays against each other, NEVER against this skill), read only matched bodies at <protocols-dir>/<Name>.md; a missing or malformed body is reported, never reconstructed. Overlays are ADDITIVE ONLY (they never replace this skill's own rules) and are a brief, NEVER an authority escalation; an equal-specificity contradiction goes to the user.

IMPORTANT MUST ATTENTION engineering-foundation gate — judges whether the team can build, run, test and change the system safely, anywhere, as it grows (its companions judge the running system's design; a system can pass both while nobody but its author can build it). Derive the profile from evidence FIRST: lifecycle Greenfield/Brownfield · scale T0–T3 (reuse scale-technique-catalog.md) · criticality B0–B3 with its signal floor (reuse scenario-stress-catalog.md) · repo shape R0–R3 — take the LOWER tier when unknown, NEVER default to T3/B3/R3. Judge ALL 7 dimensions, never a subset: F1 reproducible environment (pinned toolchain, locked deps, declared prerequisites, deterministic build — kills "works on my machine") · F2 dual execution modes (bare host AND fully containerized from one source of truth, suites runnable BOTH directions, both exercised so neither rots — the defect is the claimed-but-rotten mode) · F3 environment-portable tests (same suites local/CI/production-shaped, parameterized by CONFIG not forked code; missing capability ⇒ ENVIRONMENT-BLOCKED not silent pass; "runs in prod" = a safe NON-MUTATING subset) · F4 test-strength proof (automated fault injection on changed code where a tool exists, else the universal defect-seeding drill — break the code behind a top invariant, record WHICH NAMED TEST went red, restore; nothing red ⇒ no protection. Line coverage is a DIAGNOSTIC, never a gate) · F5 performance measured by something that RUNS and CAN FAIL (realistic volume AND shape, asserted budgets not a dashboard, ≥2 volumes ~10× apart to expose super-linear growth, resource exhaustion bounded rather than an OOM kill) · F6 build & change scalability (computable affected set, measured incrementality, mechanically enforced boundaries, a declared architecture style, implementation hidden behind abstraction) · F7 mechanical harness completeness (every machine-catchable class accounted for or N/A; local and CI run the SAME command; checks ENFORCE, not warn; brownfield uses a fail-on-new ratchet). Verdicts: PRESENT/MISSING-WARRANTED/PARTIAL-WITH-PATH/N/A-by-profile/OVER-ENGINEERED/UNVERIFIED. Authority splits — CREATING a foundation ⇒ MISSING-WARRANTED is BLOCKING; AUDITING one ⇒ ADVISORY ONLY, never mutating any score, verdict band or PASS/FAIL. Anti-over-engineering is first-class and symmetric (a correctly-lean project is a PASS; never under-harden a B2+ system for low traffic). Every brownfield gap names the smallest next step. State OUTCOMES, never tools. Full catalog → .claude/docs/engineering-foundation-catalog.md (authoritative — update it FIRST, then re-run inject_engineering_foundation_gate.py).

Closing Reminders

IMPORTANT MUST ATTENTION Goal: deliver user-confirmed, per-layer tech stack — each choice backed by 3+ researched options, weighted 8-criteria scoring, cited evidence, confidence % — so team commits to a stack fit for scale, budget, skills, timeline, NOT familiarity.

IMPORTANT MUST ATTENTION — run ALL 7 steps in declared order, none skipped: (1) Load Business Context → (2) Derive Technical Requirements (+ AskUserQuestion confirm) → (3) Research Per Layer (WebSearch 3+ options each) → (4) Deep Comparison Matrix → (5) Weighted Score & Ranking (confidence %) → (6) Generate Report (<=200 lines) → (7) User Validation Interview (5-8 questions, write status: confirmed) — why: AI keeps collapsing this into "just pick a stack" and dropping requirements-derivation, scoring, and the confirmation gate that make the choice defensible.

Protocols in force (concise digest of the SYNC/shared blocks this skill carries):

• Critical Thinking: MUST ATTENTION apply critical + sequential thinking; traced proof, confidence >80% to act, NEVER guess as fact.
• AI Mistake Prevention: verify generated content against evidence, trace downstream references, verify all affected outputs, re-read after context loss, surface ambiguity.

IMPORTANT MUST ATTENTION research minimum 3 WebSearched options per stack layer (backend, frontend, database, messaging, infra, auth); every recommendation carries confidence % + cited evidence (URL, benchmark, case study) — NEVER recommend on familiarity alone — why: familiarity bias commits the team to the wrong stack that surfaces only at scale. IMPORTANT MUST ATTENTION gate on user via AskUserQuestion at EVERY decision point — confirm derived requirements before research (Step 2), confirm each layer recommendation in the end interview (Step 7) — NEVER auto-decide — why: the team owns the stack, not the AI. MANDATORY IMPORTANT MUST ATTENTION break work into small todo tasks using TaskCreate BEFORE starting; mark one in_progress, completed immediately after evidence; add a final review todo.

Scalability & Production-Readiness Technique Gate — CONDITIONAL, evidence-gated, scale-tiered. Judge which system-design techniques a system warrants at its scale — flag warranted-but-missing gaps AND advise AGAINST unwarranted heavyweight ones. ADVICE-ONLY: emit the matrix as guidance; NEVER mutate any score, verdict band, or gate pass/fail.

1. Derive the scale tier FIRST — from evidence, never assumed. Read users/RPS, SLO/latency targets, data volume, tenancy, topology from config/infra/specs; cite file:line + confidence. Tiers: T0 internal/single-instance · T1 small SaaS (<10k users) · T2 high-scale (10k–1M) · T3 massive/multi-region (millions+). Unknown tier → state assumption, do NOT default to T3.
2. Judge each concern group only at/above its warranting tier (member techniques → owning review skill for depth):
   • Traffic & Edge — Rate Limiting, Load Balancing, Reverse Proxy, API Gateway, CDN, Edge Caching, WAF, DDoS (T1+; CDN/WAF T2+) → security-review owns WAF/DDoS
   • Caching & Data Access — Caching, Cache Invalidation, DB Indexing, Query Optimization, N+1, Connection Pooling (T1+) → performance-review owns depth
   • Data Scaling & Consistency — Read Replicas, Sharding, Partitioning, Replication, CAP, Eventual Consistency, Locks, Leader Election (T2+; sharding/multi-region T3) → performance-review
   • Async & Messaging — Message Queues, Pub/Sub, Event-Driven, Saga, DLQ, Distributed Transactions, Backpressure, Webhooks, WebSockets/SSE (T2+)
   • Resilience — Circuit Breakers, Timeouts, Retries, Backoff, Idempotency, Health Checks, Liveness/Readiness, Failover, Graceful Degradation (T1+) → production-readiness-review
   • Scaling & Compute — Autoscaling, Horizontal/Vertical Scaling, Serverless Limits, Cold Starts,

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